Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $24.26   7.554%   $26.0926   $26.09   $26.10   $26.10  
  Purchase #2 $194.61   9.557%   $213.2089   $213.21   $213.20   $213.20  
  Purchase #3 $236.72   8.416%   $256.6424   $256.64   $256.65   $256.60  
  Purchase #4 $243.79   8.426%   $264.3317   $264.33   $264.35   $264.30  
  Purchase #5 $233.26   5.358%   $245.7581   $245.76   $245.75   $245.80  
  Purchase #6 $228.38   8.416%   $247.6005   $247.60   $247.60   $247.60  
  Purchase #7 $174.79   9.393%   $191.208   $191.21   $191.20   $191.20  
  7 purchase totals = $1,335.81       $1,444.8422   $1,444.84   $1,444.85   $1,444.80